How Heart Monitor gave 90,000 users a complete picture of their health

The problem with wearable data is fragmentation

Heart Monitor had built a health tracking app with 90,000+ active users across iOS and Android. Their users were already tracking workouts, sleep, and recovery, but that data lived in six separate ecosystems. Garmin users saw Garmin data. Apple Health users saw Apple Health data. None of it talked to each other inside the app.

Each provider runs its own OAuth flow, its own data model, its own rate limits. Building native integrations for all of them would have required months of engineering time and an ongoing maintenance commitment the team could not absorb. The providers change their APIs. Auth tokens expire in different ways. Data formats differ even for the same metric across devices.

Per-user pricing does not work at scale

Commercial wearable APIs price per connected user. At 90,000 users with a large free tier, that model would have made the feature economically unviable before it shipped. The cost of offering wearable connectivity would have outpaced revenue from the users most likely to connect a device.

Open Wearables is MIT licensed and self-hosted. There are no per-user fees. The cost of connecting the ten-thousandth user is the same as connecting the first. That pricing model made the feature viable across the entire user base, not just the paid tier.

One API. Six providers. Normalized from day one.

Heart Monitor integrated Open Wearables through a single REST API. OAuth flows, token refresh, and data sync are all handled by the platform. On the receiving end: normalized, deduplicated health data in a consistent schema regardless of which device the user connected. Steps from Garmin look the same as steps from Apple Health. Sleep stages from Oura arrive in the same format as sleep stages from Whoop.

The platform ships with native SDKs for iOS and Android, so users connect their devices through an in-app OAuth flow without leaving the app or navigating to a third-party screen. Connection takes seconds. Data appears immediately.

The technology stack

Heart Monitor runs on Flutter for cross-platform mobile, with Hasura and GraphQL handling the backend data layer. Wearable data flowing through Open Wearables needed to map cleanly into that existing schema. Momentum provided implementation consulting to align the Open Wearables data model with the Hasura setup, working through specific field mappings, relationship structures, and sync patterns before the integration went live.

On the infrastructure side, Open Wearables deploys via Docker Compose. Heart Monitor ran it within their own environment with a configuration tuned for their provider set: Apple Health, Google Health Connect, Samsung Health, Garmin, Polar, and Strava. The platform handles provider-specific edge cases, including differences in how each provider handles historical data backfill, incremental sync, and permission scopes.

What Momentum delivered

Momentum built and maintains Open Wearables as a fully open-source platform covering all major wearable providers. Beyond the platform itself, the team provided Heart Monitor with implementation consulting throughout the integration: data model alignment between the Open Wearables schema and the existing Hasura backend, provider-specific technical guidance, deployment configuration, and post-launch support for sync edge cases and provider API changes.

That combination, an open-source platform with no licensing costs and hands-on consulting from the team that built it, gave Heart Monitor a path to production that a typical commercial integration partner could not offer. The platform handles the infrastructure complexity. Momentum handles the edge cases. The Heart Monitor team owned the build.

How the implementation came together

The process started with a documentation and platform handoff from the open-source repository. Before writing integration code, the team focused on data model alignment: mapping the existing health data structures to the normalized Open Wearables schema. Getting that right upfront meant the integration itself was straightforward.

Provider integration and testing followed, working through each supported device to confirm sync behavior, edge cases, and data accuracy. Momentum stayed available throughout for questions on provider-specific quirks and deployment configuration. The full process, from first SDK setup to production deployment, took one Heart Monitor engineer under a week.

Data stays where it belongs

Routing biometric data through third-party clouds increases compliance surface area and erodes user trust. Heart Monitor deployed Open Wearables on their own infrastructure. All user health data stays within their environment. No third-party routing. Full audit capability. The self-hosted model also means the integration is not affected by upstream pricing changes or service availability from a commercial API provider.

What shipped

90,000+ users now connect their wearables directly inside the app. Device data appears alongside existing health data without switching apps or manual logging. Six providers are live in production and running reliably. The normalized data layer is in place for the next phase: richer health scoring and personalized recommendations built on data the team fully controls.